package org.apache.lucene.search.spans;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import java.util.Collection;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.ToStringUtils;

/** Matches spans near the beginning of a field. */
public class SpanFirstQuery extends SpanQuery {
    private SpanQuery match;
    private int end;

    /** Construct a SpanFirstQuery matching spans in <code>match</code> whose end
     * position is less than or equal to <code>end</code>. */
    public SpanFirstQuery(SpanQuery match, int end) {
        this.match = match;
        this.end = end;
    }

    /** Return the SpanQuery whose matches are filtered. */
    public SpanQuery getMatch() {
        return match;
    }

    /** Return the maximum end position permitted in a match. */
    public int getEnd() {
        return end;
    }

    public String getField() {
        return match.getField();
    }

    public Collection getTerms() {
        return match.getTerms();
    }

    public String toString(String field) {
        StringBuffer buffer = new StringBuffer();
        buffer.append("spanFirst(");
        buffer.append(match.toString(field));
        buffer.append(", ");
        buffer.append(end);
        buffer.append(")");
        buffer.append(ToStringUtils.boost(getBoost()));
        return buffer.toString();
    }

    public Spans getSpans(final IndexReader reader) throws IOException {
        return new Spans() {
            private Spans spans = match.getSpans(reader);

            public boolean next() throws IOException {
                while (spans.next()) { // scan to next match
                    if (end() <= end)
                        return true;
                }
                return false;
            }

            public boolean skipTo(int target) throws IOException {
                if (!spans.skipTo(target))
                    return false;

                if (spans.end() <= end) // there is a match
                    return true;

                return next(); // scan to next match
            }

            public int doc() {
                return spans.doc();
            }

            public int start() {
                return spans.start();
            }

            public int end() {
                return spans.end();
            }

            public String toString() {
                return "spans(" + SpanFirstQuery.this.toString() + ")";
            }

        };
    }

    public Query rewrite(IndexReader reader) throws IOException {
        SpanFirstQuery clone = null;

        SpanQuery rewritten = (SpanQuery) match.rewrite(reader);
        if (rewritten != match) {
            clone = (SpanFirstQuery) this.clone();
            clone.match = rewritten;
        }

        if (clone != null) {
            return clone; // some clauses rewrote
        } else {
            return this; // no clauses rewrote
        }
    }

    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (!(o instanceof SpanFirstQuery))
            return false;

        SpanFirstQuery other = (SpanFirstQuery) o;
        return this.end == other.end && this.match.equals(other.match) && this.getBoost() == other.getBoost();
    }

    public int hashCode() {
        int h = match.hashCode();
        h ^= (h << 8) | (h >>> 25); // reversible
        h ^= Float.floatToRawIntBits(getBoost()) ^ end;
        return h;
    }

}
